Industrial fan and blower : Introduction

Fan, blower uses gases to perform the same fuction that pumps do with liquids. Each of these devices transfer mechanical energy from a prime mover into an increase in fluid energy. Fan and blower accomplish this as blades mounted on a rotating shaft rotor move the gas (usually air) within the fluid system. The system’s resistance to flow results in an increase in pressure across the device from inlet to discharge. A fan is designed to operate against a very small pressure rise (up to about 8 in. of water, If the rise is between 8 in. of water and about 1atm, the device is called a blower.

The primary function of a fan and blower are to

1. Circular air within a given space.
2. Deliver air to or exhaust air from a given space.
3. Push air through ducts used in ventilation, heating, or air-conditioning systems.

Axial and mixed flow design fan

The two most common types of fans are the axial flow and mixed flow designs. Figure 1 and 2 show an axial exhaust fan and an axial tube fan, respectively. These electric motor driven fans are avialable in both belt and direct drive with propeller diameters ranging from 12 to 60 in. Flow rate capacities vary from 1,000 to 77,000 cfm (cubic feet per minute), and static pressures go up to 1.5 in. of water.

Figure 1 Axial exhaust fan

Figure 2 Axial tube fan

Typical applications include spray booths, exhaust hoods, duct installation, removal of corrosive fumes and nonabrasive dust, and general factory ventilation. Figure 3 show a mixed flow design fan that combines the lightweight, inline features of the axial design with the added benefits of static pressure capability up to 8 in. of water and lower noise levels.

Figure 3 mixed flow fan

Centrifugal blowers : Introduction

A centrifugal blowers that functions similarlity to a centrifugal pump is shown in figure 1. Air enters the center opening in the housing in an axial direction, then the blades of the rotating impeller forces the air radially outward, resulting in an increase in kinetic energy. As the high velocity air enters the volute shaped portion of hte housing, some of the kinetic energy is converted into pressure energy for provideing the increased pressure necessary to deliver air to the external system. Figure 1b shows the impeller, which contains eight flat-shaped, radial blades. This particular design can handle flow rates up to 3600 cfm and static pressure up to 20 in. of water.

Figure 1 Centrifugal blower (Courtesy of American Fan Co. Fairfield Ohio)

What is the compressors ?

A compressors is a machine that compresses air or another type of gas from a low inlet pressure (usually atmospheric) to a higher desired pressure level to meet system requirement by providing a mean to reduce the volume of the gas. Compressors are either positive displacement unit (reciprocating piston, rotary screw , or rotary vane types) or dynamic (axial flow with rotating blades mounted on a rotor or centrifugal with blades mounted on a rotating impeller). We will provide detailed information in the next article.